1. Field of the Invention
The present invention relates to an imaging apparatus, and, more particularly, to a method for calibrating an imaging apparatus for scanning a document.
2. Description of the Related Art
An imaging apparatus in the form of a scanner is used to generate a digital representation of a document being scanned. Such a document may include any of a variety of media types, such as paper, card stock, etc., and may be regular (e.g., rectangular) or irregular in shape, and on which there is formed, for example, text, graphics or a picture, e.g., a photo, or a combination thereof. Typically, a color scanner generates three channels of data, e.g., red, green and blue (RGB), in generating a scanned image of the document. Separation of a background associated with a backing surface of the scanner from a foreground, i.e., the scanned image, associated with the document has been a significant problem that those practicing in the imaging art continue to address.
Distinguishing between background and foreground is particularly problematic when the background and the foreground both have the same color, such as white. For example, this problem routinely arises when the image of a white document is placed in front of a white background. More specifically, when a target document, such as business card, having a white perimetrical region is scanned against a white document pad, it may be difficult to distinguish the boundaries of the business card from the background formed by the white document pad. Knowing the boundaries of the scanned document is useful because that increases the accuracy of skew correction. Knowing the boundaries of the scanned document also enables the accurate placement of the contents of the document with respect to a printed output.
Most current scanners come with some type of skew correction and content placement software. However, such scanners use the content of the scanned image as a guide, and sometimes such content-based guidance can be misleading. For example, in a cropped image, when some of the elements are lost with respect to the background, the skew correction becomes faulty. Using a colored document pad, e.g., other than white, does not solve the problem, but only shifts the problem in the color spectrum, since this solution will fail when the scanned image includes a perimetrical color that is the same as the color of the background.